Inhalers are commonly used for delivery of a wide range of medicaments. The inhaler holds a canister of medicament, the canister being actuated e.g. by compression to deliver a dose of medicament through a mouthpiece to a user. The inhaler may be provided with an actuation mechanism to actuate the canister automatically and thus dispense a dose of medicament. Some known actuation mechanisms are breath-actuated, so that they operate in response to inhalation by a user. This ensures that a dose of medicament dispensed on actuation of the canister is supplied whilst the user is inhaling. This is particularly useful for those users who may find it difficult to co-ordinate the dispensing of a dose of medicament, by for example, the actuation of a button, with inhaling the dose.
A known breath-actuated inhaler has an actuation mechanism operable by compression of a canister of medicament to deliver a dose of medicament in response to inhalation by a user. The actuation mechanism comprises a loading mechanism to bias compression of the canister. A triggering mechanism holds the loading mechanism against compression of the canister. When delivery of a dose of medicament is required, the triggering mechanism releases to allow compression of the canister in response to inhalation by the user. An actuating means is connected to a cover for the mouthpiece and is responsive to the closing movement of the cover for re-setting the actuation mechanism. Such an arrangement results in the components of the trigger mechanism not being loaded when the inhaler is not in use. When the cover is closed, critical force is redirected from the triggering mechanism during storage (cap closed). Over time, loading of critical components can quicken the onset of material creep, resulting in mechanical failure of the inhaler and its subsequent inability to deliver a dose of medicament after a number of uses. This situation can be extremely dangerous for the user in an emergency when it is vital that the inhaler deliver a dose when required.